Mix tomatos,broth,butter,sugar,onion and heat. Simmer about a half hour or so.
Add soda (to cut the acid and not curdle the milk).
Heat the milk in the micro until fairly hot then add just a couple drops to the soup and see if it curdles. If it does, then add another half tsp of soda first and/or heat milk bit more. Curdling is the only prob with making tom soup. Good luck and enjoy. Remember try not to boil soup once the cream is in there.